Nopales are the green pads of edible cacti. You can readily purchase them at Mi Pueblo. They definitely have needles, but the workers at the grocery store have their own peeling station and will have them peeled and ready for customers. If you insist on peeling your own, make sure you wear two pairs of gloves, because the needles act like hooks and unsheath themselves into your skin if you get pricked.
The flesh of the plant cooks similar to okra. When heat is applied it will exude a thickening agent. Either cook the diced vegetable quickly or for a long period of time so you don’t end up with a vegetable covered in goo. No matter how much you cook it though, it will maintain it’s crunchy texture. The vibrant green will dissipate, but nopales is often paired with garlic and an herb called epasote. Please remember to add this herb near the end of the cooking process, or all the flavor will dissipate into the air. I hope you try some and pair it with our mole tamales.